1. Field of the Invention
The present invention relates to water supply treatment systems, and particularly to a wastewater treatment system and method that removes biodegradable fats, oil, grease, solids, organic contaminants, nutrients, pathogens and the like from wastewater generated in residential homes, commercial businesses, industrial facilities, municipal facilities, agricultural facilities and the like.
2. Description of the Related Art
In order to protect the environment and promote public health, communities typically require wastewater treatment. The discharge of untreated wastewater is not suitable, since it gives rise to numerous environmental concerns, such as the pollution of surface and groundwater resources. Untreated wastewater contains organic matter and nutrients that, if left untreated and not removed from the waste stream, can result in environmental pollution. Thus, when untreated wastewater is released into either aboveground bodies of water or subsurface drainfields, the level of dissolved oxygen in the receiving waters begins to deplete, which endangers the water bodies themselves, along with the resident plant and aquatic life. Additionally, in developing nations, where potable water is scarce, it is often desirable to recover as much reclaimable water as possible from wastewater, rather than disposing of both the wastewater and the contaminants.
To treat wastewater, communities in highly populated areas commonly collect wastewater and transport it through a series of underground pipes to a large, centralized wastewater treatment plant. However, there are several problems associated with large, centralized treatment plants. Centralized wastewater treatment plants are designed and rated for processing a specific flow rate of wastewater per day, typically expressed as the rated capacity of the plant, and all treatment plants have a maximum flow rate capacity. Thus, if a centralized treatment plant receives more wastewater on a particular day than what the plant was designed to handle, problems are encountered. For example, when a treatment plant receives larger-than-normal amounts of untreated raw wastewater, treatment performance decreases and partially treated or untreated wastewater is released into a body of water, such as a river, in order not to exceed the amount of wastewater the plant was designed to handle.
As noted above, discharge of this untreated wastewater into bodies of water will endanger and kill resident plant and aquatic life in the water. Untreated wastewater also contains a number of disease pathogens that are extremely harmful to humans. For example, untreated wastewater is one of the leading causes of dysentery, which can be life threatening. Thus, if a significant amount of untreated wastewater is discharged into a body of water, that body of water will become unavailable for human consumption. On the other hand, if the treatment plant processes the larger-than-normal amounts of untreated wastewater, instead of diverting a portion into a body of water, the influx of untreated wastewater would wash away the bacteria populations or biomass used by the plant to treat the untreated wastewater, which would disrupt the entire biological treatment process of the plant. Further, as noted above, wastewater treatment is particularly needed in developing nations, and such large-scale treatment plants may not be available.
In rural areas and in developing nations, construction of centralized wastewater treatment plants may be too expensive to build and maintain. In addition, the cost of connecting residences and businesses in rural areas to a centralized treatment plant via sewage lines may be impracticable due to the greater distance between the those residences and businesses. In such areas, septic systems are usually utilized to treat wastewater. A septic tank is typically a large tank located underground on an owner's property. Septic tanks are categorized as continuous flow systems because wastewater flows into the septic tank at one end, and the same amount of wastewater that entered will exit the tank at the other end. The purpose of a septic tank is to provide a minimal amount of anaerobic treatment and to retain any solids in the wastewater to allow only the liquid wastewater effluent to pass through to prevent drain field disposal lines from becoming clogged. However, since the wastewater leaving the septic tank has only been minimally treated, the wastewater will be a detriment to the environment due to its organic and nutrient contaminants, as noted above, and may not be recovered as reclaimed water. Furthermore, as solids build up inside the septic tank, a phenomenon known as periodic upset may occur, causing solids to flow out of the septic tank and into the field lines connected to the tank. Eventually, these field lines will clog due to the buildup and carryover of solids. When this occurs, the field lines have to be cleaned or replaced, if possible, which means destruction to a portion of the owner's property as well as increased expense to the owner. A more extreme condition would be the failure of the drain field without an adequate replacement area on the property.
Further, it has been found that certain soils are only capable of receiving and dispersing a limited amount of wastewater, given the particular soil structure, geology, and groundwater conditions. In this instance, practice has shown that a highly treated wastewater can be discharged to drainfields possessing limited hydraulic and/or soil treatment capacity. Furthermore, a high quality effluent can be reclaimed and used for secondary purposes, such as irrigation, industrial rinse and cooling, and grey water uses, for example.
Centralized wastewater treatment systems that treat over 1,500 gallons per day typically utilize either concrete, steel or fiberglass tanks to house the systems. These materials have been utilized for decades, due to the unavailability of other options. Concrete and steel, due to their particular material properties, are highly subject to corrosion and are not suited to withstand the corrosive gases and fluctuations in pH common in wastewater and wastewater treatment.
Further, both concrete and steel tanks are difficult and expensive to fabricate, transport and install. The average life expectancy of a concrete or steel wastewater tank is only between twenty and thirty years. Furthermore, to date, the only tank material option for large wastewater treatment systems over 100,000 gallons per day is concrete. Fiberglass, although a more tolerant material with a longer life expectancy, is limited in its detailing capabilities and delaminates when subjected to a sharp pressure point or conditions of constant friction.
Fiberglass tanks are typically constructed utilizing pre-developed molds and are relatively inflexible in adjustment to specific project requirements. This inflexibility results in additional required tankage, yard piping and mechanical equipment, thus resulting in increased maintenance and operational issues and expenses.
Additionally, steel, concrete and fiberglass tanks are all relatively difficult to repair when damaged. An additional option for wastewater treatment systems under 1,500 gallons per day is the utilization of rotationally or injection molded plastic tankage as the housing. Such tanks are commonly used for septic tanks, grease traps and small treatment systems, however, the overall majority of these tanks are prone to crushing when emptied and are limited in size due to the pre-developed molds. It would be desirable to form such tankage from a material that would alleviate these problems.
Thus, a wastewater treatment system and method solving the aforementioned problems is desired.